The present invention relates to filter systems for purifying the exhaust gases of internal combustion engines.
A typical engine exhaust filter system includes a housing, which has an inlet and an outlet and defines an exhaust flow path, and a filter element disposed in the exhaust flow path to trap pollutants such as particulate materials and to prevent them from being discharged into the atmosphere. The exhaust gas of an internal combustion engine may enter the filter system through the inlet, pass through the filter element, and exit the housing through the outlet. An engine exhaust filter system generally uses seals to prevent bypass of the exhaust gas around the filter element.
A challenge facing the designers of engine exhaust filter systems is to find suitable seal materials. Seals used in exhaust filter systems are exposed to severe operating conditions. For example, the filtration of the engine exhaust gases may occur at high temperatures, such as temperatures of 400xc2x0 F. or greater. A regenerative exhaust filter system for diesel engines may produce even higher temperatures, which are generally 1,000xc2x0 F. or greater. Diesel exhaust filter systems are used to trap pollutants such as soot particles in the exhaust gases. As the particulates accumulate in the filter system, they may clog the filter and increase the resistance of the filter to exhaust flow, resulting in excessive engine back pressure. Excessive engine back pressure can lead to an increase in fuel consumption, and, in extreme cases, to engine shut-off or failure. Thus, it is desirable to intermittently regenerate the filter to remove the particulates, for example, by combusting the particulates at temperatures of 1,000xc2x0 F. or greater.
Seal materials in exhaust filter systems may also experience chemical corrosion. Engine exhaust gases may contain chemicals such as acid-forming gases, which may be very corrosive when combined with high temperatures. Corrosion may shorten the usefull life of the seals, creating leakage in the exhaust filter systems.
Another challenge facing the designers of engine exhaust filter systems is to design exhaust filter seals that are strong and reliable. The reliability of the seals is important because if the seals fail, the pollutants will be able to bypass the filter element and will be discharged into the atmosphere.
The seal materials commonly used in Diesel exhaust filter systems often cannot meet the requirements of heat or chemical resistance. For example, adhesives used to seal the filter element generally cannot withstand the operating temperature and chemical corrosion for the entire life of the filter system, and leakage often occurs as a result.
The present invention overcome many of the problems of conventional exhaust filter systems.
According to one aspect of the invention, an engine exhaust filter comprises a housing and a pleated filter element. The housing includes an inlet and an outlet and defines an exhaust gas flow path between the inlet and the outlet. The pleated filter element is disposed in the exhaust gas flow path, and includes a filter medium and at least first perforated filter support member. The pleated filter element comprises materials that are resistant to temperatures of 400xc2x0 F. or greater. The filter medium is disposed adjacent to the first perforated filter support member, and includes a portion that extends beyond the first perforated filter support member. The extended portion of the filter medium comprises a seal that prevents or reduces unfiltered exhaust gas bypass of the filter element.
According to another aspect of the invention, an engine exhaust filter comprises a housing, a pleated filter element and a compression assembly. The housing includes an inlet and an outlet and defines an exhaust gas flow path between the inlet and the outlet. The pleated filter element is disposed in the exhaust gas flow path and includes a filter medium and at least a first perforated filter support member. The pleated filter element comprises materials that are resistant to temperatures of 400xc2x0 F. or greater. The filter medium is disposed adjacent to the first perforated filter support member and includes a portion that extends beyond the first perforated filter support member. The compression assembly compresses the extended portion of the filter medium such that the filter medium comprises a seal. The seal prevents or reduces unfiltered exhaust gas bypass of the filter element.